PISCES FISHES. 505 



apophyses derived from the spine (Jig. 226). The zone, represent- 

 ing the scapulary apparatus, consists of a single piece, which surrounds 

 the body, and on each side supports the bones of the fore-arm. The 

 enormously developed pectoral fin is composed of the carpus, amaz- 

 ingly augmented in size, and of the no less remarkable hand which 

 in the Skate is made up of an immense number of fingers or rays, 

 and forms by itself nearly half the circumference of the body. 



The pelvis, or cartilaginous framework that supports the hinder 

 extremities, i. e. the ventral fins, is a single transverse piece of 

 cartilage quite detached from the rest of the skeleton : it expands 

 on each side into a broad plate, to which the fin, the representative 

 of the foot of higher animals, is appended, and likewise in the male 

 it gives attachment to additional organs called claspers, the use of 

 which will be explained in another place. 



The anterior portion of the spine in the Skate is not as yet 

 divided into distinct pieces ; and, even in the posterior part, the 

 number of vertebral arches is twice as great as that of the separate 

 bodies of the vertebrse. 



In all the Chondropterygii the ribs are mere rudiments, and in 

 some cases can scarcely be said to exist at all. 



The Sturgeons (Sturionidai) form a kind of connecting link 

 between the osseous and cartilaginous fishes, and in them a 

 large swimming-bladder exists, from which is obtained the va- 

 luable material called isinglass : but in the Sharks and Rays this 

 organ is not found ; consequently, especially in the tribe last men- 

 tioned, it is xmly by means of the vigorous flappings of their enor- 

 mous hands that these ground-fishes are able to raise themselves 

 from the bottom. The disposition and relative importance of 

 different parts of the muscular system, is, therefore, necessarily 

 changed to meet these altered circumstances : the muscles of the 

 trunk, which in osseous fishes formed the great agents in loco- 

 motion, become now of secondary importance ; while those of the 

 pectoral fins, so feebly developed in the Perch, are massive and 

 powerful in proportion to the unwieldy size of the anterior extre- 

 mities. Another peculiarity in the skeleton of the Chondro- 

 pterygii is observable in the construction of the caudal fin, which 

 even in the Sturgeon and the Shark, notwithstanding the import- 

 ance which this organ still maintains in those genera as an instru- 

 ment of locomotion, begins to differ very remarkably from the tail 

 of an osseous fish. It is true that it still exhibits great expansion 

 in a vertical direction, and to a superficial observer, if examined 



